The present invention relates generally to water filtration equipment, and more particularly relates to a modular water filtration system.
Water filtration can help prevent blockage and potential wear in water sprinkler systems, valve systems and drip systems due to the presence of small particulates in water, such as sand, algae or other organic material, or the like. Typically two or more 3 to 10 foot diameter rounded tanks of media filters, also known as sand filters, are used by farms and municipal water systems to clean water of such material from rivers and lakes by forcing the water through a container filled with small particulate matter, preferably small, sharp edged, particulate filter material such as a uniformly sized, crushed sand, or a variety of different types and sizes of particulate materials. Such media filters are cleaned by back flushing, typically through an under drain. The force of the water going backwards through the filter lifts and separates the media, which frees the debris and washes it out through a flush valve. However, for a typical tank system, back flushing of one tank can require over 50% of the water flow, which can lower the water pressure of the system, causing slow action of the back flush valve, so that in some cases an expensive pressure sustaining valve must be used, which wastes water and causes longer flush times to achieve a maximum cleaning of the filter. During back flushing, in order to loosen the particulate filter material and suspend each particle of filter material in order to release the filterable impurities trapped in the particulate filter material, it is commonly necessary to use back flush flow rates greater than filtration flow rates, which can require a separate pump for back flushing, or introduction of air in the back flush liquid to lift the particulate filter material.
One conventional type of media filter is known that includes self-graded coarse-to-fine granular filter media for up-flow filtration, down-flow filtration, or filtration by combined up and down flow to a central exit. A down-flow media filter typically includes a perforated diaphragm or plate under the particulate filter material, while an up-flow filter typically includes perforated diaphragms or plates under and over the particulate filter material, allowing liquid to pass through the perforations, while preventing loss of the filter media. Down-flow filters typically include a tank containing a particulate filter material such as sand, with an inlet receiving pressurized water and an outlet for the filtered water. Following back flushing, the particulate filter material settles with the largest, fastest settling particles of filter material at the bottom and the finest, slowest settling particles of filter material at the top. During filtration, smaller filterable impurities in the liquid are filtered out by the smaller particles of filter material at the top of the filter, with very little of the filterable impurities being filtered by the larger particles of filter material at the bottom of the filter, and the remaining solids in the liquid build up on the top of the filter. Up-flow filters can be more practical and efficient than down-flow filters, because as the liquid to be filtered is pumped into the filter material from the bottom, larger filterable impurities are trapped in the coarser layer of filter material at the bottom, and smaller filterable impurities are trapped in the finer layers of filter material. The filterable impurities are more evenly distributed throughout the particulate filter material and the pressure drop is more evenly distributed across the particulate filter material, so that flow rates can be much higher than in a down-flow filter for the same pressure drop. However, the filtration rate of up-flow filters is commonly limited by the necessity of providing an upper perforated diaphragm or plate for holding the particulate filter material in place.
One conventional filter system is known that includes a set of modules, each including screen assemblies and filter media sandwiched between the screen assemblies, and multiple control assemblies, with each control assembly being provided to control flow through the corresponding module. A given module is bypassed when the given module becomes occluded, and the occluded module is back flushed by providing a reverse flow through the screen assemblies and the filter media. Another conventional filter system is known that includes a modular water filtration and back flush assembly, with a reservoir sectioned into an upper supply chamber and a lower drain chamber by modular, horizontally co-planar filter cells. A carriage assembly is selectively positioned over an individual cell and a back flush hood is lowered to isolate the modular cell. Water is pumped upwardly out of the hood to expand and flush the filter media, with jetwash probes and a baffle plate being used. Each cell is sequentially backwashed on a continuous basis, allowing uninterrupted operation of the other filtration modules.
It would be desirable to provide a water filter system including a plurality of media filter tank modules controlled by a single controller, and a back flush system requiring flushing of only one of the plurality of filter tank modules at a time to minimize pressure loss in the system flow, and not requiring pressure sustaining valves, to allow quick and efficient back flushing, with a minimum amount of back flush water. It would also be desirable to provide a modular water filter system with “union” type connections that can be hand tightened for easy installation and removal, and that can be disassembled quickly for rapid and easy servicing. It would also be desirable to provide a modular water filter system having dimensions similar to existing steel and stainless steel tank media filter systems, to allow the replacement of existing media filter systems by the modular water filter system of the invention. It would also be desirable to provide a light weight, modular water filter system that allows design and construction of a system for the exact gallons per minute required, and that allows for addition of filter tank modules to increase capacity, as needed. The present invention meets these and other needs.